A surprising number of workers leave their computers on at night after they leave. The combined energy usage of even modern, energy-efficient systems is significant, as shown in this video. What do you do when it's quitting time?

Nigel Upchurch's graphic demonstration of the energy used by Germany's share of computers left on overnight is eye-opening in its own way, but there are ways to actually use your computer smartly while you're sleeping. Still, some of us may be restricted in what we can do to our work machines while we're gone, due to IT wanting to keep update channels open, or other users jumping onto our systems.